Various alkaline based solutions have previously been employed to remove scale from metal surfaces. For example, Webster et al., U.S. Pat. No. 2,458,661 discloses a fused molten alkali salt solution for removing oxide scale and the like from metal surfaces resulting from the forming operation. Further, Shoemaker et al., U.S. Pat. No. 3,260,619 discloses a different molten alkali salt solution to overcome certain problems associated with the disclosed solution in the Webster Patent. However, both these patents contemplate the use of a further conventional acidic bath to remove conditioned scale on the metal surface which results from treatment following the molten alkali solution bath. Such acidic baths include, for example, sulfuric acid, hydrochloric acid which may be in the form of sodium chloride added to sulfuric acid, nitric acid, hydrofluoric acid and the like, alone or in combination, maintained at elevated temperatures, for example, in excess of about 100.degree.F (37.degree.C). It is the problems associated with these acid baths which the present invention intends to overcome by the provision of a gluconate caustic mixture. Although gluconate mixtures are generally known for the removal of rust and some ferrous scale, none have been applied in the field of alloy processing following salt bath conditioning.
The paramount problem associated with acidic solutions for removing conditioned scale on metal surfaces is that of solution disposal. First, disposal is expensive due to the substantial tonnage of such acids used in the descaling process. Further, disposal of such solutions adds to the presently ever-growing pollution problem. In addition to the problem of disposal, acidic solutions, even though dilute, tend to attack the metal surface. Such attack not only creates an undesirable effect on the metal surface, but adds to disposal problems because of greater metal loss within the descaling operation. Further, the use of acidic descaling solutions requires that the metal be rinsed following the molten alkali bath, since alkali carryover has a deleterious effect on the acid solution.
Accordingly, it is a primary object of the instant invention to provide a non-acidic solution and method for removing conditioned scale from the surface of various metals.
Another object of this invention is the provision of a descaling solution which does not present a pollution problem upon disposal.
A further object of this invention is providing a solution which is stable, exhibits a good life and rejects metal buildup in the form of a precipitate.
Additionally, it is an object of the present invention to provide a solution which is soluble in water and will offer no particular rinsing problems.